1. Field of the Invention
The present invention relates to a fuel hose connection structure for connecting a fuel hose and a tubular mating member, such as a metal or resin pipe, in a fluid-tight condition to thereby suppress permeation of gasoline to the exterior thereof from a connected portion thereof, as well as to a fuel hose for use in the hose connection structure.
2. Description of the Related Art
Conventionally, a fuel hose of such a type assumes the form of a multilayer hose as disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. 6-190974. Specifically, the conventional fuel hose includes an outer layer of rubber, and an inner layer of a resin or a metal formed on the inner wall of the outer layer, excluding an axial end portion of the outer layer into which a mating pipe is inserted. Since the inner layer is hard, when a mating pipe is fitted into the inner layer, sufficient sealing performance therebetween will not be maintained. Thus, a connection structure of the fuel hose avoids overlapping of the inner layer and the mating pipe, but is designed such that an end of the mating pipe inserted into the outer layer abuts an end portion of the inner layer.
According to the connection structure, permeation of gasoline to the exterior thereof can be prevented by means of the inner layer of low gasoline permeability and the mating pipe extending in succession to the inner layer. Also, since the end portion of the outer layer into which the mating pipe is inserted is not lined with the inner layer, an insertion load which arises during insertion of the mating pipe is reduced accordingly. Thus, a predetermined low gasoline permeability is established by means of the inner layer and the mating pipe inserted into the outer layer up to the position of the inner layer. Also, work efficiency in insertion of the mating pipe into the fuel hose is enhanced. However, the fuel hose connection structure involves slight permeation of gasoline through a contact portion between the inner layer and the mating pipe, and thus fails to satisfy a strict requirement for advanced low gasoline permeability.
Japanese Patent Application Laid-Open (kokai) No. 8-294979 discloses a fuel hose (see FIG. 17) including a fluoroplastic tube 82, a protector 81 for covering the fluoroplastic tube 82, and a seal rubber 83 of low gasoline permeability bonded through vulcanization to the inner wall of an end portion of the fluoroplastic tube 82 into which a mating pipe is fitted. When the mating pipe is fitted into the fuel hose, the seal rubber 83 of low gasoline permeability lies between the fluoroplastic tube 82 and the inserted mating pipe, thereby reliably suppressing permeation of gasoline and thus satisfying a strict requirement for advanced low gasoline permeability.
However, since the mating pipe is inserted into the fluoroplastic tube 82, which is hard, in spite of the presence of the seal rubber 83 therebetween, an insertion load which arises during insertion of the mating pipe is very high, resulting in impaired work efficiency in insertion of the mating pipe. Also, since the seal rubber 83 is of low gasoline permeability and is thus expensive, the fuel hose becomes expensive. Furthermore, in order to prevent relative movement between the fluoroplastic tube 82 and the seal rubber 83 during insertion of the mating pipe, they must be bonded together, thereby causing a further increase in the cost of the fuel hose.
Japanese Patent Application Laid-Open (kokai) No. 8-312844 discloses another conventional fuel hose (see FIGS. 18 and 19), which includes an outer hose portion 91 of rubber having a first bellows portion 92 and a first straight cylindrical portion 93 extending from at least one end of the first bellows portion 92, and an inner hose portion 94 of resin disposed within the outer hose portion 91 substantially coaxially and having a second bellows portion 95 and a second straight cylindrical portion 96 extending from at least one end of the second bellows portion 95. The fuel hose is configured in the following manner: the second straight cylindrical portion 96 is disposed within the first straight cylindrical portion 93; a ring member 97 is disposed inside the second straight cylindrical portion 96, whereas a clamp member 98 is disposed to surround the outer surface of the first straight cylindrical portion 93 in order to tighten the first straight cylindrical portion 93 radially inward; and the first straight cylindrical portion 93 and the second straight cylindrical portion 96 are held between the ring member 97 and the clamp member 98 to thereby be integrated into a single unit. The publication also discloses a fuel hose in which either the ring member or the clamp member is omitted. A mating pipe 99 is fitted into the outer hose portion 91 of the fuel hose until the mating pipe 99 abuts an axial end portion of the second straight cylindrical portion 96 of the inner hose portion 94, thereby forming a connection structure of the fuel hose and the mating pipe.
Since the outer hose portion 91 is made of rubber, the mating pipe 99 can be easily fitted thereinto, and the mating pipe 99 and the outer hose portion 91 are sealed against each other. Furthermore, an end portion of the mating pipe 99 abuts an end portion of the inner hose portion 94 made of a resin impermeable to gasoline, thereby preventing permeation of gasoline through the connected end portion to the exterior of the fuel hose connection structure.
However, in the fuel hose connection structure, sealing is established merely through abutment of the end portion of the mating pipe 99 against the end portion of the inner hose portion 94 made of a resin impermeable to gasoline. As a result, as shown in FIG. 19, when a load is imposed on the mating pipe 99 or the fuel hose, a resultant relative movement between the mating pipe 99 and the fuel hose cannot be absorbed at the abutment portion, resulting in formation of a gap between the end of the inner hose portion 94 and that of the mating pipe 99. A slight amount of gasoline permeates through the gap. Thus, the conventional fuel hose connection structures cannot satisfy a strict requirement for advanced low gasoline permeability when the requirement is in effect.
An object of the present invention is to solve the above-mentioned problems in the conventional fuel hose connection structure and fuel hose and to provide an inexpensive fuel hose connection structure capable of satisfying a strict requirement for advanced low gasoline permeability and facilitating insertion of a mating material into a fuel hose, as well as a fuel hose for use in the fuel hose connection structure.
To achieve the above object, the present invention provides a fuel hose connection structure in which a fuel hose has a straight insertion end portion at one axial end thereof and a tubular mating member is connected to the insertion end portion in a fluid-tight condition. The fuel hose comprises a tubular outer layer made of an elastic material; an annular groove portion formed on the inner wall of the outer layer at an axially inward end of the insertion end portion, the annular groove portion being formed coaxially with the inner wall along the entire circumference of the inner wall; a thin-walled inner layer made of a resin material of low gasoline permeability and fixedly bonded to the entirety of a portion of the inner wall of the outer layer, the portion including at least the groove portion and extending axially inward from the groove portion; and an annular seal member fitted tightly into the groove portion lined with the inner layer. The mating member has an annular engagement protrusion formed at one end portion thereof along the entire circumference in such a manner as to protrude radially outward. The mating member is inserted under pressure from the one end portion into the insertion end portion of the fuel hose such that the engagement protrusion is engaged with the groove portion while pressing radially outward on the seal member fitted into the groove portion. The fuel hose connection structure further comprises an annular clamp member fitted onto the outer layer at a position located axially outward with respect to the groove portion and adapted to tighten the outer layer securely so as to connect the inserted mating member and the fuel hose in a fluid-tight condition.
In the present invention, the engagement protrusion of the mating member is tightly fixed, via the inner layer and the annular seal member, to the groove portion formed on the inner wall of the outer layer at an axially inward end of the insertion end portion of the outer layer, whereby permeation of gasoline can be sufficiently prevented. Also, most of a press-fit path of the fuel hose along which the mating member is inserted under pressure is formed of the outer layer, which is soft. Insertion of the mating member involves radially outward expansion of the inner layer, which is hard, at merely one end portion of the path; i.e., at the groove portion. Thus, an insertion load which arises during insertion of the mating member can be low.
As a result, the present invention sufficiently prevents permeation of gasoline at a connection of the fuel hose and the mating member and thus can satisfy a strict requirement for advanced low gasoline permeability. Since an insertion load which arises during insertion of the mating member into the fuel hose is low, work efficiency in the insertion is enhanced. The seal member fitted into the groove portion assumes the form of a ring, which is axially short, and thus is inexpensive as compared with the conventional seal rubber.
Preferably, in the fuel hose connection structure, the outer layer and the inner layer protrude coaxially and radially inward at a position adjacent to and located axially inward with respect to the groove portion so as to form an annular positioning protrusion. The positioning protrusion reliably blocks an axially inward movement of the seal member and the mating member beyond an engagement end position; i.e., beyond the groove portion. That is, the positioning protrusion reliably prevents displacement of the seal member and the mating member from the groove portion. Also, the positioning protrusion enables a user to know that insertion of the mating member is completed.
The present invention further provides a fuel hose having a straight insertion end portion at one axial end thereof, comprising a tubular outer layer made of an elastic material; an annular groove portion formed on the inner wall of the outer layer at an axially inward end of the insertion end portion, the annular groove portion being formed coaxially with the inner wall along the entire circumference of the inner wall; a thin-walled inner layer made of a resin material of low gasoline permeability and fixedly bonded to the entirety of a portion of the inner wall of the outer layer, the portion including at least the groove portion and extending axially inward from the groove portion; and an annular seal member fitted tightly into the groove portion lined with the inner layer. A tubular mating member having an annular engagement protrusion formed at one end portion thereof along the entire circumference in such a manner as to protrude radially outward is inserted under pressure from the one end portion into the insertion end portion of the fuel hose such that the engagement protrusion is engaged with the groove portion while pressing radially outward on the seal member fitted into the groove portion. An annular clamp member is fitted onto the outer layer at a position located axially outward with respect to the groove portion in such a manner as to tighten the outer layer securely so as to connect the inserted mating member and the fuel hose in a fluid-tight condition.
The annular groove portion formed on the inner wall of the insertion end portion of the outer layer at an axially inward end of the insertion end portion is lined with the inner layer and has the annular seal member fitted tightly therein. Thus, through engagement with the groove portion of the engagement protrusion of the mating member inserted under pressure into the fuel hose, permeation of gasoline can be sufficiently prevented. Also, most of a press-fit path of the fuel hose along which the mating member is inserted under pressure is formed of the outer layer, which is soft. Insertion of the mating member involves radially outward expansion of the inner layer, which is hard, at merely one end portion of the path; i.e., at the groove portion. Thus, an insertion load which arises during insertion of the mating member can be low. As a result, the present invention sufficiently prevents permeation of gasoline at a connection of the fuel hose and the mating member and thus can satisfy a strict requirement for advanced low gasoline permeability. Since an insertion load which arises during insertion of the mating member into the fuel hose is low, work efficiency in the insertion is enhanced. The seal member fitted into the groove portion assumes the form of a ring, which is axially short, and thus is inexpensive as compared with the conventional seal rubber.
Preferably, in the fuel hose, the outer layer and the inner layer protrude coaxially and radially inward at a position adjacent to and located axially inward with respect to the groove portion so as to form an annular positioning protrusion. The positioning protrusion reliably blocks an axially inward movement of the seal member and the mating member beyond an engagement end position; i.e., beyond the groove portion. That is, the positioning protrusion reliably prevents displacement of the seal member and the mating member from the groove portion. Also, the positioning protrusion enables a user to know that insertion of the mating member is completed.
The present invention further provides a fuel hose connection structure in which a fuel hose has a straight insertion end portion at one axial end thereof and a tubular mating member is connected to the insertion end portion in a fluid-tight condition. The fuel hose comprises a tubular outer layer made of an elastic material; an annular groove portion formed on the inner wall of the outer layer at an axially inward end of the insertion end portion, the annular groove portion being formed coaxially with the inner wall along the entire circumference of the inner wall; an inner layer of low gasoline permeability assuming the form of a thin-walled tube made of resin and disposed coaxially within the outer layer, the inner layer having an axially outward end portion fitted into the groove portion; and an annular seal member fitted tightly into the groove portion into which the axially outward end portion of the inner layer is fitted. The mating member has an annular engagement protrusion formed at one end portion thereof along the entire circumference in such a manner as to protrude radially outward. The mating member is inserted under pressure from the one end portion into the insertion end portion of the fuel hose such that the engagement protrusion is engaged with the groove portion while pressing radially outward on the seal member fitted into the groove portion. The fuel hose connection structure further comprises an annular clamp member fitted onto the outer layer at a position located axially outward with respect to the groove portion and adapted to tighten the outer layer securely so as to connect the inserted mating member and the fuel hose in a fluid-tight condition.
In the present invention, the engagement protrusion of the mating member is tightly fixed, via the inner layer and the annular seal member, to the groove portion formed on the inner wall of the outer layer at an axially inward end of the insertion end portion of the outer layer, whereby permeation of gasoline can be sufficiently prevented. Also, most of a press-fit path of the fuel hose along which the mating member is inserted under pressure is formed of the outer layer, which is soft. Insertion of the mating member involves radially outward expansion of the inner layer, which is hard, at merely one end portion of the path; i.e., at the groove portion. Thus, an insertion load which arises during insertion of the mating member can be low.
As a result, the present invention sufficiently prevents permeation of gasoline at a connection of the fuel hose and the mating member and thus can satisfy a strict requirement for advanced low gasoline permeability. Since an insertion load which arises during insertion of the mating member into the fuel hose is low, work efficiency in the insertion is enhanced.
Preferably, in the fuel hose connection structure, the outer layer protrudes coaxially and radially inward at a position adjacent to and located axially inward with respect to the groove portion so as to form an annular positioning protrusion. The positioning protrusion reliably blocks an axially inward movement of the seal member and the mating member beyond an engagement position; i.e., beyond the groove portion. That is, the positioning protrusion reliably prevents displacement of the seal member and the mating member from the groove portion. Also, the positioning protrusion enables a user to know that insertion of the mating member is completed.
The present invention further provides a fuel hose having a straight insertion end portion at one axial end thereof, comprising a tubular outer layer made of an elastic material; an annular groove portion formed on the inner wall of the outer layer at an axially inward end of the insertion end portion, the annular groove portion being formed coaxially with the inner wall along the entire circumference of the inner wall; an inner layer of low gasoline permeability assuming the form of a thin-walled tube made of resin and disposed coaxially within the outer layer, the inner layer having an axially outward end portion fitted into the groove portion; and an annular seal member fitted tightly into the groove portion into which the axially outward end portion of the inner layer is fitted. A tubular mating member having an annular engagement protrusion formed at one end portion thereof along the entire circumference in such a manner as to protrude radially outward is inserted under pressure from the one end portion into the insertion end portion of the fuel hose such that the engagement protrusion is engaged with the groove portion while pressing radially outward on the seal member fitted into the groove portion. An annular clamp member is fitted onto the outer layer at a position located axially outward with respect to the groove portion in such a manner as to tighten the outer layer securely so as to connect the inserted mating member and the fuel hose in a fluid-tight condition.
In the present invention, the axially outward end portion of the inner layer is fitted into the groove portion formed on the inner wall of the insertion end portion of the outer layer at an axially inward end of the insertion end portion, and the annular seal member is fitted tightly thereinto. Thus, through engagement with the groove portion of the engagement protrusion of the mating member inserted under pressure into the fuel hose while pressing radially outward on the seal member, permeation of gasoline can be sufficiently prevented. Also, most of a press-fit path of the fuel hose along which the mating member is inserted under pressure is formed of the outer layer, which is soft. Insertion of the mating member involves radially outward expansion of the inner layer, which is hard, at merely one end portion of the path; i.e., at the groove portion. Thus, an insertion load which arises during insertion of the mating member can be low.
As a result, the present invention sufficiently prevents permeation of gasoline at a connection of the fuel hose and the mating member and thus can satisfy a strict requirement for advanced low gasoline permeability. Since an insertion load which arises during insertion of the mating member into the fuel hose is low, work efficiency in the insertion is enhanced.
Preferably, in the fuel hose, the outer layer protrudes coaxially and radially inward at a position adjacent to and located axially inward with respect to the groove portion so as to form an annular positioning protrusion. The positioning protrusion reliably blocks an axially inward movement of the seal member and the mating member beyond an engagement position; i.e., beyond the groove portion. That is, the positioning protrusion reliably prevents displacement of the seal member and the mating member from the groove portion. Also, the positioning protrusion enables a user to know that insertion of the mating member is completed.